TY - JOUR
T1 - The Effect of Suprathermal Protons in the Heliosheath on the Global Structure of the Heliosphere and Heliotail
AU - Heerikhuisen, Jacob
AU - Zirnstein, Eric J.
AU - Pogorelov, Nikolai V.
AU - Zank, Gary P.
AU - Desai, Mihir
N1 - Publisher Copyright:
© 2019. The American Astronomical Society..
PY - 2019/3/20
Y1 - 2019/3/20
N2 - In the interaction between the solar wind (SW) and the local interstellar medium, various processes create ions with energies up to ∼10 keV that are out of thermal equilibrium with the "core" population. Wave-particle interactions tend to isotropize the velocity distributions, but the collisionless nature of the SW precludes thermalization. Suprathermal protons can charge-exchange with interstellar hydrogen, producing energetic neutral atoms that are seen by the Interstellar Boundary EXplorer spacecraft. We have developed a model for the presence of several suprathermal populations in the SW downstream of the heliospheric termination shock. The model uses magnetohydrodynamics to satisfy the first three moments of the total ion distribution, and couples these through charge-exchange to neutral hydrogen, conserving mass, momentum, and energy in the combined system. The proton population is separated into a cool core and three suprathermal populations, and hydrogen atoms may charge-exchange with protons from any of those four populations. The phase-space properties of the pick-up ions are selected based on data and theoretical considerations. In this paper we quantify the impact of suprathermal protons on the global structure of the heliosphere by comparing our new model to a traditional Maxwellian fluid model, and a kappa-distribution model. We find that the differences in momentum and energy transfer rates from the protons onto neutral hydrogen between the models leads to different plasma properties in the heliotail, and also changes the size of the heliosphere. Including the energy-dependent charge-exchange cross section into the collision integrals reduces the magnitude of these differences.
AB - In the interaction between the solar wind (SW) and the local interstellar medium, various processes create ions with energies up to ∼10 keV that are out of thermal equilibrium with the "core" population. Wave-particle interactions tend to isotropize the velocity distributions, but the collisionless nature of the SW precludes thermalization. Suprathermal protons can charge-exchange with interstellar hydrogen, producing energetic neutral atoms that are seen by the Interstellar Boundary EXplorer spacecraft. We have developed a model for the presence of several suprathermal populations in the SW downstream of the heliospheric termination shock. The model uses magnetohydrodynamics to satisfy the first three moments of the total ion distribution, and couples these through charge-exchange to neutral hydrogen, conserving mass, momentum, and energy in the combined system. The proton population is separated into a cool core and three suprathermal populations, and hydrogen atoms may charge-exchange with protons from any of those four populations. The phase-space properties of the pick-up ions are selected based on data and theoretical considerations. In this paper we quantify the impact of suprathermal protons on the global structure of the heliosphere by comparing our new model to a traditional Maxwellian fluid model, and a kappa-distribution model. We find that the differences in momentum and energy transfer rates from the protons onto neutral hydrogen between the models leads to different plasma properties in the heliotail, and also changes the size of the heliosphere. Including the energy-dependent charge-exchange cross section into the collision integrals reduces the magnitude of these differences.
KW - ISM: atoms
KW - Sun: heliosphere
KW - solar wind
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U2 - 10.3847/1538-4357/ab05e3
DO - 10.3847/1538-4357/ab05e3
M3 - Article
AN - SCOPUS:85064437513
SN - 0004-637X
VL - 874
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 76
ER -